<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<meta name="viewport" content="width=device-width,initial-scale=1,minimum-scale=1,maximum-scale=1,user-scalable=no" />
		<title></title>
		<style type="text/css">
		div{
			width: 100%;
			height: 100px;
		}
			@media  screen and (min-width: 1280px){
				div{
					background: red;
				}
			}
			
			@media  screen and (min-width: 768px) and (max-width: 1279px) {
				div{
					background: green;
				}
			}
			
			@media  screen and (max-width:767px ) {
				div{
					background:blue ;
				}
				
			}
		</style>
	</head>
	<body>
		<div></div>
		<div class="box"></div>
		<div class="box"></div>
		<div class="box"></div>
		<div class="box"></div>
	</body>
</html>
